The present invention relates to optical structures. More specifically, the present invention relates to a system and method for coupling and redirecting optical energy between two optical waveguides oriented at a predetermined angle relative to each other, such as an angle having a magnitude of ninety degrees.
Communication networks rely on optical networks to transmit complex communication data, such as voice and video traffic. This voice and video traffic propagated over the optical network usually takes the form of high frequency optical signals that have a relatively high bit rate.
To support these high frequency optical signals, optical networks typically comprise a large volume of fiber optic cables that extend over long distances. Because the fiber optic cables extend over long distances, these cables usually encounter obstacles or redirection that are common with any utility line. In other words, the fiber optic cables of optical networks can be routed under streets and highways with multiple twists, turns, and junctions. The fiber optic cables also can extend between buildings in above-ground supporting environments, such as between telephone poles that have several changes in direction.
In many of these routing situations, the fiber optic cables are directed at various angles relative to the origination or starting point of the fiber optic cable. To change direction or to connect a fiber optic cable to another fiber optic cable, an operation known as splicing can be performed to connect fiber optic cables together.
The splicing of fiber optic cables can be a tedious and time-consuming process. For example, splicing fiber optic cables is similar to handling cables with diameters that approach the diameter of a human hair. For a typical splice of a fiber optic cable, two separate fiber optic cables are cut. Next, their ends are polished and then their ends are compressed together.
While the ends are compressed together, it is necessary for the geometric center of these human hair-size cables to be properly aligned. If these human hair-like fiber optic cables are not properly aligned, substantial losses in optical power can occur at the splice. In other words, optical energy leaving one fiber optic cable is not completely transferred into the other fiber optic cable because of the misalignment of the fiber optic cables relative to each other.
After splicing, the junction or splice can be placed in one of several different types of protective enclosures to protect the splice from exposure to environmental effects. For example, the splice can be placed within a splice box, a conduit, or within a breakout panel. These protective enclosures can be placed in a manhole, in a pedestal, or in drop points adjacent to the subscribers of the optical network. Protecting splices with enclosures demonstrates that splicing of fiber optic cables can be a costly and time consuming process that does not guarantee optical coupling efficiency.
In addition to the problems associated with splicing, fiber optic cables cannot be bent at very large angles such as ninety degrees without suffering substantial optical power losses. To prevent such power losses, fiber optic cables are gradually routed around the obstacles at angles substantially less than ninety degrees. The gradual routing of fiber optic cables requires an even distribution of the weight for the additional cable needed to make this cable routing.
The gradual routing can also relieve the physical stresses within a fiber optic cable that are associated with the bending of the fiber optic cable at these gradual angles. Stress caused by the gradual routing of a fiber optic cable should be minimized in order to eliminate micro-bending. Micro-bending can cause greater losses at longer optical wavelengths, such as the optical wavelengths that support dense wavelength division multiplexing.
The gradual routing of fiber optic cables at angles substantially less than ninety degrees around objects is usually referred to as a wide bending radius technique. Another major drawback of larger bending techniques, in addition to the problems of stress and the amount of cable to perform the operation, is that such techniques require a substantial amount of space. To alleviate the problems of fiber optic cable splice connections and wide bending radius techniques, optical connectors have been proposed to couple one fiber optic cable oriented in a first direction and a second fiber optic cable oriented in a second direction. However, conventional optical connectors are usually permanent in nature, meaning that adjustments to the connector and any optics contained in the connector cannot be made during installation in the field. If there are any problems with the optics contained within the conventional optical connector, the connector usually must be discarded instead of repaired. Further, if any adjustments to the optics within the optical connector are necessary, such adjustments cannot be made in the field since the connectors are typically designed to permanently encase or house the optics contained therein.
Another drawback of conventional optical connectors is that very few of these conventional optical connectors can withstand the harsh operating environments of optical cables. For example, optical connectors can be exposed to high temperatures as well as fluids for certain applications. The optical connectors must be able to withstand harsh temperatures and to keep out any fluids that may come in contact with the fiber optic cables and the connector.
Accordingly, there is a need in the art for a system and method for coupling and redirecting optical energy between two optical waveguides oriented at a predetermined angle relative to each other. There is also a need in the art for a system and method for coupling and redirecting optical energy between two optical waveguides that permits adjustments to the optics housed in the optical coupler while in the field or operating environment. In other words, there is a need in the art for an optical coupler that has fielded adjustable optics to permit the adaptation of the optical coupler to various types and sizes of optical waveguides.
Further, there is also a need in the art for an optical coupler that is impervious to any liquids that are present in the operating environment of the optical couple and optical waveguides. There is also a need in the art for optical couplers that can withstand harsh operating environments where the optical coupler can be subjected to high temperatures.
A further need exists in the art for optical couplers that employ optical waveguide connectors that can comprise the size and dimensions of any one of industry standard connectors known in the art. There is also a need in the art for optical couplers that can meet or exceed industry standards for optical connectors.
Additionally, the need exists in the art for optical couplers that can maximize the optical energy transfer between two optical waveguides, while minimizing any back reflection or other optical return losses. There is also a need in the art for optical couplers that provide automatic core-to-core alignment of optical waveguides in free space. Further, there is also a need in the art for optical couplers that can provide a junction or connection point between different types of optical waveguides, such as single mode optical fibers, or optical waveguides, such as multi-mode optical fibers.
The present invention is generally drawn to a system and method for coupling and redirecting optical energy between two optical waveguides oriented at a predetermined angle relative to each other. More specifically, the present invention provides an optical waveguide coupler that can be adjusted in the field and which can couple and redirect optical energy from a first optical waveguide oriented in a first position into a second optical waveguide oriented in second position different from the first position. That is, the optical waveguide coupler according to one exemplary aspect of the present invention can be assembled and readjusted while in its operating environment, outside of any typical manufacturing environment.
There are at least two features of the present invention that make this system and method for coupling and redirecting optical energy between two optical waveguides a substantial improvement over the art: 1) the mechanical properties of the optical coupler; and 2) the discrete optics that are positioned within the connector housing and connectors. Regarding the mechanical properties of the optical coupler, the optical coupler can comprise a connector housing in one exemplary embodiment that can be made from metal. Exemplary metals include, but are not limited to, steel, copper, nickel, or aluminum. The material for the housing is usually selected such that its coefficient of expansion is less than the coefficient of expansion for the first cover or second cover or both. The connector housing can also be made from polycarbonate material, such as a polycarbonate material sold under the tradename DELRIN. Although the connector housing can take the form of a cube structure, other shapes of the connector housing are not beyond the scope of the present invention.
A first cover that attaches to the connector housing and supports a mirror positioned within the connector housing can be made from a polycarbonate material, such as a polycarbonate material sold under the tradename DELRIN. Alternatively, in another inventive aspect, the first cover can be made from a composite ceramic material, such as a ceramic material sold under the tradename ALLTEMP. A second cover, opposing the first cover, also attaches to the connector housing and can be made from the same materials as the first cover.
The first cover and second cover can have a stepped region for contacting walls of the connector housing such that the first and second covers can attach to the connector housing with a snapped fit. More specifically, the first and second covers can have a coefficient of thermal expansion relative to the coefficient of thermal expansion of the connector housing such that the first and second covers expand at a more rapid rate relative to any expansion of the connector housing.
The xe2x80x9csnapped-fitxe2x80x9d of the first and second covers can allow the optical waveguide coupler of the present invention to be field adjustable, unlike static and permanent optical connectors of the prior art. Further, this xe2x80x9csnap-fitxe2x80x9d between the covers and the connector housing can also make the optical coupler impervious to penetration by any liquids that are present outside of the optical coupler. In other words, the first and second covers can form a waterproof or airtight seal with the connector housing. While the first and second covers snap together to form this seal, the covers can also be removed after assembly such that the optics within the connector housing can be adjusted.
The connectors that attach the optical waveguides to the connector housing can also be made from polycarbonate material, sold under the tradename DELRIN. In another inventive aspect, the connectors can be made from a composite ceramic material sold under the tradename ALLTEMP. In addition to supporting the optical waveguides, the connectors can also support and hold one or more discrete optics in predetermined and precise positions. For example, the connectors can support lenses that focus the optical energy propagating through the optical waveguides.
The connectors can comprise dimensions of any one of industry standard connectors known in the art. For example, the connectors can comprise ferrule connectors (FC) that have a threads for a screw-type connection between the connector housing and the connectors. In another inventive aspect, the connectors can comprise subscriber connectors (SC) that have a square bayonet snap connection. Alternatively, the connectors can comprise lucent connectors (LC). Other connector types include fiber distribution data interface (FDDI) and straight tip (ST) connectors.
The materials selected for the connector housing, first and second covers, and connectors can allow the optical coupler to withstand harsh operating environments. For example, the optical coupler could be subjected to high temperatures produced from either the surrounding environment or the optical energy transferred between the optical waveguides or both. More specifically, the materials selected for the connector housing, first and second covers, and connectors can allow the optical coupler to withstand high temperatures, such as between xe2x88x9280 degrees Celsius and +85 degrees Celsius.
Because the optical coupler can withstand wide ranges of temperature as remain impervious to liquids outside the optical coupler, the optical coupler can usually meet or exceed several industry standards for optical connectors, such as BELLCORE standards. Further, the size and shape of the optical coupler and the snap-fit covers allow this device to be easily manufactured compared to other optical connectors that require permanent fasteners, such as welds and adhesives.
While the mechanical features of the present invention provide significant advantages over the prior art, the discrete optics supported by the connectors and the connector housing also provide additional advantages. The optical coupler can maximize the optical energy transfer between two optical waveguides while minimizing any back reflection or other optical return losses. The optical coupler can maximize optical energy transfer between optical waveguides disposed at an angle by providing core-to-core alignment of optical waveguides in free space.
For one aspect of the invention, the optical coupler can provide a junction or connection point between optical waveguides, such as single mode optical fibers that are positioned at a predetermined angle, such as ninety degrees, relative to each other. For another inventive aspect, the optical coupler can provide a junction or connection point between optical waveguides such as multimode optical fibers also positioned at a predetermined angle, such as ninety degrees, relative to each other. Those skilled in the art recognize that the optical coupler can be scaled or sized depending upon the type and size of the optical waveguides being coupled together.
As noted above, the optical coupler can comprise a first cover that supports a mirror. This mirror can comprise a one-hundred percent mirror that reflects or redirects optical energy received from one optical waveguide into another optical waveguide. For one aspect of the invention, the mirror can comprise a triangularly shaped solid member that is held in position by a support mechanism that is part of the first cover.
The mirror of the optical coupler forms only a portion of the inventive optical system. The other parts of the optical system can comprise at least two lenses that are supported or precisely positioned by the two connectors. Each lens comprises an aspherically shaped lens that has a planar side and a convex side. The convex side of each aspherically shaped lens can have a prescription that maximizes the collection and redirection of optical energy. The prescription of each lens is a function of the optical coupler dimensions and a function of the optical waveguide dimensions and type.
Each convex side of each lens can face the inside of the connector housing, while each planar side of each lens can be positioned to face the optical waveguide. In this way, for a first aspherical lens, substantially all of the optical energy that exits a first optical waveguide in a dispersion cone of a predetermined angle can be collimated by the first aspherical lens and then redirected or reflected by the mirror.
The optical energy that is reflected from the mirror can be propagated into a second aspherical lens where the convex side of the second aspherical lens can focus the collimated optical energy into a focal point that can correspond directly with a central region of a second optical waveguide. The focused optical energy can then be propagated away from the second aspherical lens in the second optical waveguide. In this way, the optical coupler can maximize the optical energy transfer between two optical waveguides while minimizing any back reflection or other optical return losses. The optical coupler can maximize optical energy transfer between optical waveguides disposed at an angle by providing an automatic core-to-core alignment of optical waveguides in free space that is dependent on the precise positioning of the lenses in each connector, the position of the reflecting device in the housing, and the positions of each connector relative to the housing.
According to an alternate aspect of the present invention, the optical system can comprise a solid member that includes the aspherical lenses coupled to the mirror. In other words, the optical system can comprise a single member that has the aspherical lenses and the mirror connected or bonded together. The single member and lenses can be made from an optical grade polycarbonate.